Process of evaporation.



Larisa @FJBIGE.

FLETCHER B. HOLMES, OF WOODBUBY, NEW JERSEY, ASSIGNOR TO E. I. DU FONT DE NEMOURS POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF NEW JERSEY.

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No Drawing.

To all whom it may concern Be it known that I, FLETCHER B. HOLMES, of Woodbury, in the county of Gloucester, and in the State of New Jersey, have invented a certain new and useful Improvement in Processes of Evaporation, and do hereby declare that the following is a full, clear, and exactdescription thereof.

My invention relates particularly to an improvement in processes of evaporating solutions. It is especially applicable, however, to the concentration of solutions by boiling in order to separate the solutefrom the solvent either by crystallization from the concentrated solution or by completely boiling off the solvent.

In concentrating solutions in this manner, the solvent sometimes becomes aci as the concentration progresses owing to the decomposition of a constituent of the solution. This is frequently a great disadvantage because of its effect upon the yield or quality of the final product and because of the erosion of the container in which the concentration'is being carried out. In such cases, it has previously been the practice to neutralize the free acid in the solution whenever possible b the addition of an alkali, such for examp e, as the hydrate or carbonate of sodium or potassium. or by the addition of a hydrate or carbonate of an alkaline earth, such as the hydrate or carbonate of calcium. In certain cases this is, however, not practicable. For example, in the con- 'centration of solutions of ammonium salts in water slight dissociation takes place at the high temperatures used, resulting in the formation of free acid which attacks the metal of the container and also resulting in the loss of ammonia. This free acid cannot be neutralized by the compounds previously used for this purpose and noted above, inasmuch as they rapidly decompose the ammonium salts thus setting free ammonia gas. In the concentration of solutions of ammonium salts by boiling in iron containers, it has consequently been found that it was impossible to prevent the formation offree Specification of Letters Patent.

PROCESS OF EVAPORATION.

Application filed January 14, 1914. Serial No. 812.037.

acid without the loss of ammonia, where an alkali has been used to neutralize the acid. I have discovered that if I add to solutions of this general nature an insoluble metallic hydroxid and particularly a hydroxid of a tri-valent metal, such as aluminum, and keep this hydroxid distributed throughout the solution during concentration, any free acid formed in the solution is neutralized to such an extent that very little erosion of the metal container takes place and in sucn a manner that the neutralizing hydroxid does not cause appreciable decomposition of the salts in the solution, such for example,

The freshly precipias ammonium salts. tated hydroxids are especially advantageous as they are more readily attacked by acids when in this condition. If found desirable an insoluble metallic hydroxid of a bi-valent metal may also be used for this purpose, such for example, as a hydroxid of lead.

While my invention is capable of being carried'out in many different ways, for the purpose of illustration I may state one example thereof as follows: In boiling a solution of ammonium nitrate in water in an iron container I may add to the solution a small amount of the freshly precipitated hydroxid of a tri-valent metal such as aluminum hydroxid. When the concentration is carried out in this manner, the erosion of the iron is almost entirely prevented while at the same time the aluminum hydroxid does not decompose the ammonium salt. By the use of the hydroxid I therefore prevent the deterioration of the iron aluminum to which the formula has been given.

While I have described my invention above in detail, I wish it to be understood that many changes may be made therein without departing from the spirit of my invention. v

'I claim: i

1. The process which comprises evaporating a solution having a tendency to become acid by evaporation, in the presence of an insoluble material which reduces the acidity.

2. The process which comprises evaporating a solution having a tendency to become acid by evaporation, in the presence of an insoluble hydroxid which reduces, the acidity.

3. The process which comprises evaporating a solution having a tendency to become acid by evaporation, in the presence of the hydroxid of a tri-valent metal which reduces the acidity.

4. The process which comprises evaporating a solution having a tendency to become acidby evaporation, in the presence of the freshly precipitated hydroxid of a trivalent metal which reduces the acidity.

5. The process which comprises evaporating a solution having a tendency to become acid by evaporation, in the presence of freshly precipitated hydroxid of aluminum which reduces the acidity.

6. The process which comprises evaporating a solution having a tendency to become acid by evaporation, in the presence of hydroxid of aluminum which reduces the acidity.

7. The process which comprises evaporating a solution of an ammonium salt having a tendency to become acid by evaporation, in the presence of an insoluble material which reduces the acidity.

8. The process which comprises evaporating a solution of an ammonium salt having a tendency to beconm acid by evaporation, in the presence of an insoluble hydroxid which reduces the acidity.

' 9. The process which comprises evaporating a solution of an ammonium salt having a tendency to become acid by evaporation, in the presence of the hydroxid of a trivalent metal which reduces the acidity.

10. The process which comprises evaporating a solution of an ammonium salt having a tendency to become acid by evaporation,'in the presence of the freshly precipitated hydroxid of a tri-valent metal, which reduces the acidity.

11. The process which comprises evapo- 12. The process which comprises evapo- 7 rating a solution of an ammonium salt hav ing a .tendency to become acid by evaporation, in the presence of freshly precipitated hydroxid of aluminum which reduces the acidity.

13. The process which comprises evaporating a solution of ammonium nitrate having a tendency to become acid by evaporation, in the presence of an insoluble material which reduces the acidity.

14. The process which comprises evaporating a solution of ammonium nitrate having a tendency to become acid by evaporation, in the presence of an insoluble hydroxid which reduces the acidity.

15. The process which comprises evaporating a solution of ammonium nitrate having a tendency to become acid by evaporation, in the presence of the hydroxid of a tri-valent metal which reduces the acidity.

16. The process which comprises evaporating a solution of ammonium nitrate having a tendency to become acid by evaporation in the presence of the freshly precipitated hydroxid of a tri-valent metal which reduces the acidity. V

17. The process which'comprises evaporating a solution of ammonium nitrate havlng a tendency to become acid by evaporation, in the presence of hydroxid of aluminum which reduces the acidity.

18. The process which comprises evaporating a solution'of ammonium nitrate having a tendency to become acid by evaporation in the presence of freshly precipitated hydroxid of aluminum which reduces the acidity.

19. The process which comprises evaporating in an iron vessel, a solution having a tendency to become acid by evaporation. in the presence of an insoluble material which reduces the acidity.

20. The process which comprises evaporating in an iron vessel, a solution having a tendency to become acid by evaporation, in the presence of an insoluble hydroxid which reduces the acidity.

21. The process which comprises evaporating in an iron vessel, a solution having a tendency to become acid by evaporation, in the presence of the hydroxid of a tri-- valent metal which reduces the acidity.

22. The process which comprises evaporating in an iron vessel, a solution having a tendency to become acid by evaporation. in the presence of the freshly precipitated hydroxid of a tri-valent metal which redroxid. of aluminum which reduces the 10 acidity.

In testimony that I claim the foregoing I have hereunto set my hand.

FLETCHER B. HOLMES.

Witnesses:

ALEXANDER L. ROGERS, ARTHUR M. Home 

